This invention relates generally to couplers for optical fibers and is more particularly concerned with optical fiber couplers for eccentrically mounted optical fibers which are simple in construction and which are highly efficient in normal operating environments.
A recent development in communication systems involves the use of optical fibers for very high bandwidth communication channels. The use of such optical fibers, which carry light energy distributed over an area, has led to the need for a coupler which can conveniently and efficiently couple a pair of such optical fibers to each other. The difficulty in accomplishing this end is directly attributable to the cross-sectional dimensions of the optical fibers. The dimension for the light carrying portion of such optical fibers commonly is on the order of about 50 micrometers.
The coupling of optical fibers involves generally precise mechanical control of the alignment of the optical fibers to achieve low coupling losses. Furthermore, for such optical communication systems to be of general utility, the couplers associated therewith must be such as to be adaptable to use in the field. Therefore, the couplers must be rugged, yet simple in construction so as to provide physical protection for the actual optical fibers, yet allow for quick and convenient operation of the coupling function.
Various fiber-to-fiber coupling techniques are found in the prior art. Principally, these techniques may be divided into those which utilize connectors having the optical fibers precisely centered therein, such as shown and described in copending patent application Ser. No. 498,803, filed August 19, 1974, by Bridger et al. now issued as U.S. Pat. No. 3,914,880 and entitled Optical Fiber Coupler and Connector, this application being assigned to the same assignee as the instant application, and connectors wherein the optical fiber is eccentrically located, such as shown in U.S. Pat. No. 3,800,388 by Borner et al.. Both of these arrangements have certain advantages associated therewith. The concentric coupler may be snapped together in the field without need for checking for the alignment of the fiber by passage of a signal through the coupling junction. However, the efficiency of this coupling depends upon the accuracy with which the minute optical fiber is centered in the connector. Highly precise centering, of course, greatly increases the expense of the couplers. On the other hand, the eccentrically mounted optical fiber connectors require adjustment in order to effect precise alignment of the optical fibers. However, far less care is required in the assembly of the couplers to the fibers since adjustment of the relative positions is inherent within the arrangement.
The eccentrically mounted coupler configuration has suffered from another disadvantage in all prior art configurations in that because the connectors must be rotated within the coupling arrangement, distortion and scoring occur and the ability to precisely align and hold that alignment is destroyed easily.